1. Field of the Invention
The present invention relates to a technology for encoding image data.
2. Description of the Related Art
Various methods have been developed for compressing or encoding image data. Amount of image data can be reduced by compressing or encoding. Consequently, it is possible to send the original image data in a shorter time via a network, i.e., to achieve high-speed data communication, and store the original image data in a smaller storage space.
Furthermore, there is know a technology for dividing image data into a picture area and a text area, for example, as disclosed in Japanese Patent Application Laid-open No. 2003-58878. The resolution of image data of each of the picture area and the text area is converted into an appropriate resolution, and the resolution-converted image data is compressed. After that, the resolution-converted image data of the picture area and the text area are merged into one image data. By such an operation, the original image data can be compressed with high efficiency.
In this manner, compressing or encoding is effective in reducing the amount of data. Therefore, for example, when a document including a picture (such as a photo or a pattern) or a line image (such as a text or a symbol) is compressed or encoded beforehand, it is possible to store/transmit/receive the document at high speed and/or with high efficiency.
However, if image data is processed by using the technique of dividing the image data into a picture area and a text area, and if the image data of each of the picture area and the text area is compressed or encoded uniformly, it may cause degradation of the image quality.